691912009 has 2 divisors, whose sum is σ = 691912010. Its totient is φ = 691912008.

The previous prime is 691912007. The next prime is 691912021. The reversal of 691912009 is 900219196.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 673662025 + 18249984 = 25955^2 + 4272^2 .

It is a cyclic number.

It is not a de Polignac number, because 691912009 - 2¹ = 691912007 is a prime.

Together with 691912007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (691912003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345956004 + 345956005.

It is an arithmetic number, because the mean of its divisors is an integer number (345956005).

Almost surely, 2^691912009 is an apocalyptic number.

It is an amenable number.

691912009 is a deficient number, since it is larger than the sum of its proper divisors (1).

691912009 is an equidigital number, since it uses as much as digits as its factorization.

691912009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8748, while the sum is 37.

The square root of 691912009 is about 26304.2203648008. The cubic root of 691912009 is about 884.4710508104.

The spelling of 691912009 in words is "six hundred ninety-one million, nine hundred twelve thousand, nine".